1. Field of the Invention
This invention relates to the preparation of acid amides by reacting (Si, Ge or Sn substituted amino)-1,3,5-triazines, such as (N-silylated amino)-1,3,5-triazines, with acid halides.
2. Description of Related Art
Various derivatives of amino-1,3,5-triazines are described in the literature for use in a wide variety of fields. Certain of these derivatives, such as alkoxymethyl derivatives of melamine and guanamines, are useful as crosslinkers or reactive modifiers in curable compositions which contain resins having active hydrogen groups. While alkoxymethylated melamines and guanamines provide excellent results in a number of aspects, they also have the disadvantage of releasing formaldehyde as a volatile by-product under curing conditions. It has long been a desire of industry to find acceptable alternatives which do not emit formaldehyde upon cure.
One such alternative which has shown great promise is carbamate and isocyanate functional 1,3,5-triazines disclosed in U.S. Pat. Nos. 4,939,213, 5,084,541, 5,288,865, U.S. application Ser. No. 07/998,313 (filed Dec. 29, 1992), U.S. application Ser. No. 08/061,905 (filed May 13, 1993), U.S. application Ser. No. 08/138,581 (filed Oct. 15, 1993), U.S. application Ser. No. 08/239,009 (filed May 6, 1994), and U.S. application Ser. No. 08/286,835 (filed Aug. 5, 1994), all of which are commonly owned with the present application and all of which are hereby incorporated by reference herein as if fully set forth. The carbamate and isocyanate functional 1,3,5-triazines disclosed in these references have been found to be particularly useful as crosslinkers in coating compositions based upon hydroxy functional resins, with the cured coatings possessing a wide range of desirable properties.
The ability of carbamate and isocyanate functional 1,3,5-triazines to perform as efficient non-formaldehyde emitting crosslinking agents, particularly in curable coating compositions, has initiated intensive research directed towards the discovery of practical and economical processes for their production, a number of which are disclosed in the previously incorporated references. While a number of these processes have shown great promise, certain of them also have some drawbacks including, for example, the required use of expensive starting materials and/or low ultimate yield of the desired products.
In addition to the processes of the aforementioned incorporated references, it has now been surprisingly discovered that acid amides can be prepared with excellent yields by reacting (Si, Ge or Sn substituted amino)-1,3,5-triazines, such as silylated melamine, with acid halides. It has also been discovered that the use of a acid halide selected from the group consisting of oxalyl chloride, phosgene or phosgene analogs provides excellent yields of isocyanate-functional 1,3,5-triazines. The isocyanate-functional 1,3,5-triazines may be further derivatized by contacting the same with a wide variety of well-known isocyanate-reactive materials. For example, these isocyanates may be readily xe2x80x9cblockedxe2x80x9d (for example, converted to the corresponding carbamate) by adding a blocking agent (such as a hydroxyl compound) to the isocyanate-functional 1,3,5-triazine without isolating it. In addition, the isocyanates may be readily oligomerized by adding a multifunctional isocyanate-reactive compound (for example, a diol or diamine) to the isocyanate-functional 1,3,5-triazine without isolating it.
It should be noted that it is generically known to obtain isocyanates by phosgenation of silylated amines as disclosed in Mironov et al., Zh. Obshchei. Khim. 1969, 39(11), 2598-9 and Chem. Abstracts No. 66300r, Vol.72, 1970, p.328. It is, however, also well known that the amine functionality of amino-1,3,5-triazines, such as melamine, is not equivalent to other types of typical amine functionality. Significantly, melamines are among the least reactive of the xe2x80x9caminesxe2x80x9d and the most difficult to functionalize, and their behavior cannot normally be correlated to that of other known amines.
For example, most xe2x80x9ctypicalxe2x80x9d amines are highly reactive with acid halides. In a publication by E. M. Smolin and L. Rappaport entitled xe2x80x9cS-Triazines and Derivatives,xe2x80x9d Interscience Publishers Inc., New York, page 333 (1959), it is reported that attempts to react an acid halide with the amino group on a 1,3,5-triazine such as melamine were not successful. Further, attempts to functionalize amino-1,3,5-triazine often results in substitution at the nitrogen on the triazine ring. For example, it is known that the reaction of melamine with alkyl halides, such as allyl chloride, results in alkyl substitution at the nitrogen on the triazine ring resulting in isomelamine derivatives.
Indeed, it is reported in U.S. Pat. No. 3,732,223 that the well-known phosgenation of amines fails to produce isocyanate functionality when applied to amino-1,3,5-triazines. In subsequent U.S. Pat. No. 3,919,221, the phosgenation of amino-1,3,5-triazines having one or two unsubstituted amino groups attached to the triazine ring to obtain monoisocyanato and diisocyanato triazines is reported to occur under certain specified conditions. These references do not, however, suggest that (Si, Ge or Sn substituted amino)-1,3,5-triazines can be reacted with acid halides, such as phosgene, to produce acid amides, and particularly isocyanate-functional 1,3,5-triazines, in significant yields.
Surprisingly, a procedure has now been discovered in which acid halides, including phosgene (and phosgene sources) and halogenated formates, can readily and effectively be reacted with (Si, Ge or Sn substituted amino)-1,3,5-triazines to produce a corresponding acid amide, including isocyanate- and carbamate-functional 1,3,5-triazines. Moreover, the isocyanate-functional derivatives can further be readily and effectively reacted with known isocyanate-reactive materials (such as blocking agents) to produce the corresponding isocyanate-based derivatives thereof.
In accordance with the present invention, there is provided a process for preparing acid amides which, in its overall concept, comprises the step of contacting:
(a) a (Si, Ge or Sn substituted amino)-1,3,5-triazine represented by the formula: 
xe2x80x83wherein
wherein Z and Z1 are independently selected from the group consisting of hydrogen, a hydrocarbyl, a hydrocarbyloxy, a hydrocarbylthio, a group represented by the formula xe2x80x94N(Q)2, and a group represented by the formula: 
each Q is independently selected from the group consisting of hydrogen, hydrocarbyl, hydrocarbyloxy hydrocarbyl and M(R1)3, provided that at least one Q group is M(R1)3,
A is an n-functional anchor,
n is at least 2,
each Z2 is independently selected from the group consisting of hydrogen, a hydrocarbyl, a hydrocarbyloxy, a hydrocarbylthio and a group represented by the formula N(Q)2,
each M is independently selected from the group consisting of silicon, germanium and tin, and
each R1 is independently selected from substituted or unsubstituted alkyl, alkenyl, aryl, aralkyl and alkoxy groups; and
(b) an acid halide,
under reaction conditions sufficient to produce a corresponding acid amide derivative.
As indicated above, an acid amide is produced by contacting an acid halide with the (Si, Ge or Sn substituted amino)-1,3,5-triazine. An isocyanate-functional 1,3,5-triazine is produced by employing, for example, phosgene, oxalyl chloride or a phosgene analog as the acid halide. This isocyanate-functional 1,3,5-triazine may be reacted with isocyanate-reactive materials to produce various isocyanate-based derivatives. For example, the isocyanate groups may be blocked by contacting the isocyanate-functional 1,3,5-triazines with known isocyanate blocking agents, such as certain active hydrogen containing compounds. As another example, oligomers of the isocyanate-functional 1,3,5-triazines can be produced by contacting the same with multifunctional isocyanate-reactive materials such as diols and diamines. The phrase xe2x80x9cisocyanate and/or isocyanate-basedxe2x80x9d 1,3,5-triazines, in the context of the present invention, includes triazine derivatives having isocyanate functionality, isocyanate-based functionality, or a mixture of isocyanate and isocyanate-based functionality. For example, when a blocking agent is added in an amount which is less than the molar equivalent of the available isocyanate functionality, then a triazine derivative is produced having both isocyanate and blocked-isocyanate functionality.
If the acid halide employed in the present invention is a hydrocarbyl haloformate, such as an alkyl or aryl haloformate, then the resulting acid amide is a carbamate-functional 1,3,5-triazine. When the process is practiced in this manner, there is no need to add an isocyanate-reactive material as described above to obtain a 1,3,5-triazine derivative having carbamate functionality.
The process of the instant invention can also be practiced by preparing the (Si, Ge or Sn substituted amino)-1,3,5-triazine in situ. This is accomplished by mixing an amino-1,3,5-triazine and a silicon-, germanium- or tin-containing reactive compound, such as for example, chlorotrimethylsilane, along with the acid halide.
The process of this invention is advantageous because no halogenated amino-1,3,5-triazine starting materials are required. Further, the yield of the acid amide product is increased by employing the (Si, Ge or Sn substituted amino)-1,3,5-triazine compound compared to the use of an unsubstituted triazine. Moreover, the (Si, Ge or Sn substituted amino)-1,3,5 triazines, such as N-silylated melamine, can be reacted with, for example, phosgene, followed by reaction of the isocyanate with any one of a wide variety of well-known isocyanate-reactive materials to obtain an isocyanate-based 1,3,5-triazine without handling or isolation of the isocyanate triazine product. Alternatively, the (Si, Ge or Sn substituted amino)-1,3,5-triazine can be reacted with an acid halide, such as an alkyl haloformate, to directly obtain an acid halide having carbamate functionality.
A preferred use of the acid amides, including the isocyanate-functional 1,3,5-triazines and various derivatives thereof is as a crosslinking agent with polyfunctional active hydrogen containing resins such as hydroxy-functional acrylic or polyester resins, for producing curable compositions which have utility in coatings, adhesives, molding and other applications. This and other uses are disclosed in various of the previously incorporated references.
These and other features and advantages of the present invention will be more readily understood by those of ordinary skill in the art from a reading of the following detailed description.
As indicated above, the present invention is a novel process for preparing acid amides by contacting a (Si, Ge or Sn substituted amino)-1,3,5-triazine with an acid halide. The term xe2x80x9cSi, Ge or Sn substituted aminoxe2x80x9d means within the context of this invention that a silicon (Si), germanium (Ge) or tin (Sn)-containing group is bound to the amino group of an amino-1,3,5-triazine through (Si), (Ge) or (Sn). The process is carried out under reaction conditions, such as temperature, pressure and for a sufficient time, to result in the formation of the corresponding acid amide.
The term xe2x80x9cacid amidexe2x80x9d as employed herein includes the reaction products resulting from the combination of the amine group of a (Si, Ge or Sn substituted amino)-1,3,5-triazine with the non-halide portion of an acid halide. When the acid halide employed is, for example, a halo formate, the resulting acid amide is a carbamate-functional 1,3,5-triazine. On the other hand, if the acid halide employed is phosgene, oxalyl chloride or a phosgene analog, the resulting acid amide is an isocyanate-functional 1,3,5-triazine.
When an isocyanate-reactive material such as a well-known isocyanate blocking agent is added subsequent to the formation of the isocyanate-functional 1,3,5-triazine, there is obtained the corresponding 1,3,5-triazine with isocyanate-based (blocked isocyanate) functionality. More highly functional derivatives of such isocyanate-functional 1,3,5-triazines can also be produced by adding a multifunctional isocyanate-reactive material subsequent to the formation of the isocyanate-functional 1,3,5-triazine.
The (Si, Ge or Sn Substituted Amino)-1,3,5-Triazine Starting Materials
The (Si, Ge or Sn substituted amino)-1,3,5-triazine starting materials, such as tris(trimethylsilyl) melamine, i.e., N,Nxe2x80x2,Nxe2x80x3-tris(trimethylsilyl)-2,4,6-triamino-1,3,5-triazine, and oligomers thereof, can be readily prepared using standard and well known techniques to silylate, germanylate and/or tinylate the amino group(s) of amino-1,3,5-triazines.
The term xe2x80x9c(Si, Ge or Sn substituted amino)-1,3,5-triazinexe2x80x9d in the context of this invention includes a monomeric 1,3,5-triazine having at least one and preferably at least two Si, Ge or Sn substituted amino groups attached to the triazine ring (Si, Ge or Sn substituted guanamines and melamines), as well as various N-substituted oligomers of 1,3,5-triazines (e.g., dimers, trimers and tetramers) having at least two Si, Ge or Sn substituted amino groups attached to the triazine rings per molecule.
The term xe2x80x9chydrocarbylxe2x80x9d in the context of the present invention, and in the above formula, is a group which contains carbon and hydrogen atoms and includes, for example, alkyl, aryl, aralkyl, alkenyl, and substituted derivatives thereof. Likewise, the term xe2x80x9chydrocarbylenexe2x80x9d (as utilized below) refers to a divalent hydrocarbyl such as, for example, alkylene, arylene, alkenylene, and substituted derivatives thereof.
The group A in the above formula is an n-functional anchor which can, for example, be a hydrocarbon residue (e.g., a hydrocarbylene group such as a methylene group), an amino compound residue, NH, N(hydrocarbyl), O, S, CO2, NHCO2, CO(NH)2 and the like. (Si, Ge or Sn substituted amino)-1,3,5-triazines containing this A group are referred to herein as oligomeric (Si, Ge or Sn substituted amino)-1,3,5-triazines. As specific examples of such may be mentioned, for example, silylated self-condensation products of melamine-formaldehyde resins, and silylated oligomers produced by the condensation of n-moles of a melamine-formaldehyde resin with one mole of an n-functional polyol, such as trimethylolpropane.
Preferred for use in the present process, however, are predominantly monomeric (Si, Ge or Sn substituted amino)-1,3,5 triazine materials which, in the above formula, are those wherein:
at least one of Z and Z1 is a group represented by the formula N(Q)2, and the other
is selected from the group consisting of hydrogen, a hydrocarbyl, a hydrocarbyloxy,
a hydrocarbylthio and a group represented by the formula xe2x80x94N(Q)2, more preferably
wherein both Z and Z1 are N(Q)2; and
at least one Q group on each xe2x80x94N(Q)2 group is M(R1)3. For each M(R1)3 group, preferably M is silicon and each R1 is independently selected from the group consisting of substituted or unsubstituted alkyl of 1 to 20 carbon atoms, alkenyl of 3 to 20 carbon atoms, aryl of 6 to 20 atoms, aralkyl of 2 to 20 carbon atoms, arylene of 8 to 20 carbon atoms and alkoxy of 1 to 20 carbon atoms. More preferably, M is silicon and each R1 is independently selected from the group consisting of an alkyl of 1 to 6 carbon atoms, most preferably methyl.
Especially preferred for use in the process of this invention is a substantially monomeric N-silylated melamine, wherein both Z and Z1 are N(Q)2 and at least one Q group on each xe2x80x94N(Q)2 group is Si(R1)3. The most preferred substantially monomeric N-silylated melamine is N, Nxe2x80x2, Nxe2x80x3-tris(trimethylsilyl) melamine.
As mentioned previously, the (Si, Ge or Sn substituted amino)-1,3,5-triazine starting materials of this invention can be prepared by the in situ reaction of an amino-1,3,5-triazine with a (Si, Ge or Sn) reactive compound. The useful amino-1,3,5-triazines are fully disclosed in the previously incorporated patents and patent applications set forth herein. Exemplary (Si, Ge or Sn) reactive compounds can be represented by the formula W(M(R1)3)n wherein M and R1 are as previously defined, W is a leaving group and n is at least 1. Preferred leaving groups represented by W include hydrogen, halogen, halogenated acetamides and the like. Other possible leaving groups include, for example, anions of other amides, imides, carbamates, sulfonamides, sulfonimides, amines, imidates derived from imidate esters, alkyl, aryl, and aralkyl mercaptides, alkyl, aryl, and aralkyl sulfonates, perfluorosulfonates, alkyl, aryl, and aralkyl carboxylates, perfluorocarboxylates, azide, cyanide, perhaloalkyl such as trihalomethyl, alkoxy, aryloxy, aralkoxy, halogenated derivatives thereof, including perhaloalkoxy such as the trichloromethoxy derived from the reaction of silylated melamine with the phosgene equivalent di(trichloromethyl) carbonate, and the like. It is most preferred that M is silicon. Most preferred (Si, Ge or Sn) reactive compounds include for example, chlorotrimethylsilane, bis(trimethylsilyl) trifluoroacetamide, trimethylsilylimidazole, and hexamethyidisilazane.
The Acid Halides
Examples of the acid halides usable in the practice of this invention are fully set forth in previously incorporated U.S. Pat. No. 5,288,865. The preferred acid halides suitable for use in the practice of the invention include, for example, hydrocarbyl haloformates such as alkyl chloroformates and aryl chloroformates, acyl chlorides, haloalkylcarbonyl chlorides, acryloyl chlorides, carbamoyl chlorides, alkylene bis acid chlorides, phosgene and mixtures thereof.
The most preferred acid halides are methyl chloroformate, n-butyl chloroformate, n-butyl fluoroformate, phenyl chloroformate, 2-chloroethyl chloroformate, ethyl chloroformate, propyl chloroformate, isopropyl chloroformate, isobutyl chloroformate, 2-ethylhexyl chloroformate, chloroacetyl chloride, 4-chlorobutyryl chloride, acryloyl chloride, methacryloyl chloride, oxalyl chloride, ethyloxalyl chloride, benzoyl chloride, para-nitrobenzoyl chloride, acetyl chloride, stearoyl chloride, and phosgene.
A particularly preferred acid halide for use in the present invention is phosgene which is well-known to those of ordinary skill in the art as being represented by the formula ClC(O)Cl. Phosgene, as defined within the context of this invention, also includes phosgene analogs capable as serving as a phosgene source, as well as phosgene equivalents which are generally well-known to those of ordinary skill in the art. Exemplary phosgene analogs include, without limitation, diphosgene and triphosgene. Diphosgene (trichloromethyl chloroformate) and triphosgene (trichloromethyl carbonate) are represented, respectfully, by the formulas ClC(O)CCl3 and Cl3COC(O)OCCl3. Triphosgene is known by those skilled in the art to be a phosgene source. See, e.g., M. J. Coghlan and B. A. Caley, xe2x80x9cTrichloromethyl Carbonate as a Practical Phosgene Sourcexe2x80x9d Tetrahedron Letters, Vol. 30, No. 16, pp. 2033-2036 (1989). Exemplary phosgene equivalents include, without limitation, N,Nxe2x80x2-carbonyldiamidazole and dicyanocarbonyl.
The use of phosgene is most preferred in the present invention for the preparation of isocyanate-functional 1,3,5-triazines.
The Isocyanate-Reactive Materials
As mentioned earlier, isocyanate-functional 1,3,5-triazines that are prepared by the process of this invention can be post-reacted with an isocyanate-reactive material such as an active hydrogen containing compound to form isocyanate-based 1,3,5-triazine derivatives.
A wide variety of active hydrogen containing compounds are suitable for use in forming isocyanate-based derivatives, such as carbamates, and are described in detail in the previously incorporated references. For instance, the active hydrogen containing compounds employed in this process include those known to one skilled in the art which have at least one active hydrogen moiety selected from the group consisting of carboxyl, hydroxyl, thiol, sulfonamide, amido, primary amine, secondary amine, salts thereof and mixtures thereof. As preferred examples may be mentioned alcohols, phenols, oximes, hydroxamic ethers, lactams and mixtures thereof.
As a specific preferred example, carbamate-functional 1,3,5-triazine derivatives can be formed by reacting the isocyanate-functional triazines with hydroxyl group-containing compounds. As suitable hydroxyl group-containing compounds may be mentioned, for example, straight or branched monohydric or polyhydric alkanols and alkenols having 1 to 20 carbon atoms per molecule, monohydric or polyhydric cycloalkanols and cycloalkenols having 3 to 20 carbon atoms in the molecule, and monohydric and polyhydric arylalkyls having 7 to 20 carbon atoms per molecule. Further, these alcohols may also have a substituent such as a halogen atom, a cyano group, an alkoxy group, a sulfoxide group, a sulfone group, a carbonyl group, an ester group, an ether group and an amide group. Mixtures of the above are also suitable.
Preferred of the above are the aliphatic linear, cyclic, saturated, or unsaturated alcohols having 1 to 8 carbon atoms, as well as mixtures thereof. As specific preferred examples may be mentioned methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, iso-butanol, tert-butanol, pentanol, hexanol, cyclohexanol, heptanol, octanol, ethylhexyl alcohol, benzyl alcohol, allyl alcohol, ethylene chlorohydrin, ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, ethoxyethanol, hydroxyethoxyethanol, 1-methoxy-2-propanol and mixtures thereof.
Phenols are also suitable as the hydroxyl group-containing compound. As specific examples may be mentioned phenol, various alkyl phenols, various alkoxy phenols, various halogenated phenols, dihydroxybenzene, 4,4-dihydroxydiphenylmethane, various bisphenols such as bisphenol-A, and hydroxynaphthalenes. As specific preferred examples may be mentioned phenol, 2-methyl phenol, 3-methyl phenol, 4-methyl phenol, 2-chlorophenol, 3-chlorophenol, 4-chlorophenol, catechol, resorcinol, hydroquinone, and mixtures thereof.
Many of the aforementioned hydroxyl group-containing compounds are well-known isocyanate blocking agents. Other well-known isocyanate blocking agents are also suitable for use herein, and include, for example, those blocking groups which deblock at relatively low temperatures, e.g., below about 125xc2x0 C., such as an oxime of an aldehyde or ketone (e.g., methylethyl-ketoxime, acetone oxime and cyclohexanone oxime), lactam (e.g., caprolactam), hydroxyamic acid ester, imidazole, pyrazole, N-hydroxyimide (e.g., N-hydroxyphthalimide), dimethylamine, or other blocking groups such as recited in U.S. Pat. No. 4,444,954 the pertinent portions of which are incorporated by reference herein as if fully set forth.
For use as a crosslinking agent as described in various of the previously incorporated references, most preferred for the isocyanate-reactive compound are aliphatic alcohols and ether-alcohols having 1 to 18 carbons, such as methanol, ethanol, isopropanol, propanol, isobutanol, n-butanol, t-butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, lauryl alcohol, 2-ethyl hexanol, alkyl alcohol, glycidol, stearyl alcohol, ethoxyethanol and 1 -methoxy-2-propanol.
Process Conditions
In the process of the present invention, the (Si, Ge or Sn substituted amino)-1,3,5-triazine and the acid halide are contacted in a reaction system, under conditions such as temperature and pressure, and for length of time sufficient to produce the desired acid amide. The reaction system of the present invention is not limiting, and can be any reaction system, such as a vessel or container, which can be subject to the conditions required to obtain the desired acid amide.
The relative amounts of the (Si, Ge or Sn substituted amino) 1,3,5-triazine and acid halide employed in the process is generally in the range of about 1:1 to about 1:50 and most preferably in the range of about 1:3 to about 1:5 on an equivalent weight basis. The reactants may be mixed in varying amounts, but typically at least one equivalent of acid halide is used per equivalent of (Si, Ge or Sn substituted amino)-1,3,5 triazine. An excess of acid halide is preferably employed.
The reaction components may be contacted at any temperature and pressure conditions which will result in the formation of the acid amide. Preferably, the reaction temperature ranges from about 0xc2x0 C. to about 200xc2x0 C., and more preferably from about 50xc2x0 C. to about 100xc2x0 C. In addition, the reaction of the components is preferably conducted at a pressure in the range from about 0 psig to about 500 psig, and more preferably from about 0 psig to about 200 psig, depending upon the reaction temperature. At these temperatures and pressures, the reaction has been found to produce acid amides, including isocyanate-functional 1,3,5-triazine, in a period of time ranging from about 0.5 hours to about 20 hours.
The process may be carried out as a continuous or batch process. It may be carried out by simply admixing in any order, the (Si, Ge or Sn substituted amino)-1,3,5-triazine and the acid halide. Alternatively, as previously mentioned, the reaction may be carried out by admixing an amino 1,3,5-triazine, a Si, Ge or Sn-containing reactive compound and the acid halide to form the (Si, Ge or Sn substituted amino)-1,3,5-triazine in situ. The process can be carried out with or without solvents. If a solvent is employed, preferable solvents include nitrobenzene, chlorobenzene, dichlorobenzene, cyclic and acrylic ethers.
The reaction process is generally carried out under an atmosphere of an inert gas under substantially moisture free conditions. This minimizes the decomposition of the reactants and products by atmospheric moisture.
When the acid amide reaction product is obtained as a solution, the acid amide can be isolated by removing the volatiles under reduced pressure or by distillation. The acid amide can also be isolated by dissolving the product residue in a solvent and precipitating the acid amide by adding a solvent in which the acid amide is substantially insoluble. The acid amide product may also be purified by recrystallization, distillation or chromatographic techniques well known to those skilled in the art.
When isocyanate-functional 1,3,5-triazine is prepared by the above-described process, it may subsequently be reacted with the isocyanate-reactive material described herein and in various of the previously incorporated references. Generally, the isocyanate-functional 1,3,5-triazine and isocyanate-reactive material may be reacted at temperatures ranging from about xe2x88x9220xc2x0 C. to about 200xc2x0 C., and for varying times, depending on the isocyanate-reactive material. For most suitable blocking agents, the components are reacted at a temperatures ranging from about 20xc2x0 C. to about 40xc2x0 C. when adding the blocking agents. Such blocking reaction is carried out to substantial completion, generally for a time ranging from about 10 minutes to about 2 hours. The resulting isocyanate-based isocyanate-functional 1,3,5-triazines can be isolated in any desired manner, such as by filtration and distillation of the solvent.
The relative amount of isocyanate blocking agent material added to the isocyanate-functional 1,3,5-triazine is generally in the range about 3 to about 30 equivalents of isocyanate-reactive functionality per isocyanate group. Preferably, the ratio is in the range of about 3:1 to about 5:1 on such equivalent basis.
If the amount of active hydrogen containing compound added to the reaction is less than the molar equivalent of available isocyanate functionality, then the resulting 1,3,5-triazine will have a mixture of isocyanate and isocyanate-based functionality. When utilized as a xe2x80x9cblocked isocyanatexe2x80x9d crosslinking agent, it is preferred to add an amount of blocking agent which will react to form a fully blocked-isocyanate functional 1,3,5-triazine.
The examples which follow are intended as an illustration of certain preferred embodiments of the invention; and no limitation of the invention is implied.